CAS Key Laboratory of Ocean Circulation and Wave Studies, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.
Sci Rep. 2019 Feb 27;9(1):2957. doi: 10.1038/s41598-019-39596-2.
Both sporadic observations and modelling studies suggest that subthermocline eddies (SEs) exist east of the Philippines, where interhemispheric waters meet. However, effects of SEs on water mass mixing have never been observed. Here, using data from mooring and buoy deployed in the frontal region of the interhemispheric water masses, we show for the first time that the SEs act as an "underwater mixer" of intermediate waters from north and south Pacific oceans. The SEs have typical swirl speeds of 0.1~0.4 m s between 200 and 800 m depth with a dominant period of ~90 days. Variation in intermediate water salinity also had a period of ~90 days, lagging eddy speed by ~8 days. Horizontal eddy diffusivity representative of eddy mixing rate was quantified using a mixing-length framework. Horizontal eddy diffusivity had both surface and subthermocline maxima. The vertically varying eddy diffusivity can be used to improve parameterization of eddy stirring in the tropical Pacific by coarse-resolution ocean climate models. The effect of the SEs on mixing of intermediate water masses seems not resolved by available eddy-resolving ocean models typically used for this region.
既有零星观测结果，也有模式研究表明，在菲律宾东部存在次温跃层涡（SEs），这里是两半球水体交汇的地方。然而，SEs 对水团混合的影响从未被观测到。在这里，我们首次利用在两半球水体的锋区布放的锚系和浮标数据，表明 SEs 充当了来自北太平洋和南太平洋的中层水的“水下混合器”。SEs 在 200 至 800 米深度范围内的典型漩涡速度为 0.1 至 0.4 米/秒，主要周期约为 90 天。中层水盐度的变化也有一个约 90 天的周期，比涡旋速度滞后约 8 天。利用混合长度框架定量了代表涡旋混合率的水平涡旋扩散系数。水平涡旋扩散系数在海面和次温跃层都有最大值。垂直变化的涡旋扩散系数可用于改进热带太平洋粗分辨率海洋气候模型中对涡旋搅拌的参数化。现有的、通常用于该地区的、能够解析涡旋的海洋模型似乎没有解决 SEs 对中层水团混合的影响问题。
